1. Field of the Invention
The present invention relates generally to the field of modular communication plugs for terminating cables or conductors.
2. Description of Related Art
In the telecommunications industry, modular plug type connectors are commonly used to connect customer premise equipment (CPE), such as telephones or computers, to a jack in another piece of CPE, such as a modem, or in a wall terminal block. These modular plugs terminate essentially two types of cable or cordage: ribbon type cables and standard round or sheathed cables.
In ribbon type cables, the conductors running therethrough are arranged substantially in a plane and run, substantially parallel, alongside each other throughout the length of the cable. The individual conductors may have their own insulation or may be isolated from one another by channels defined in the jacket of the ribbon cable itself, with the ribbon cable providing the necessary insulation. Conversely, the conductors packaged in a standard round cable may take on a random or intended arrangement with conductors being twisted or wrapped around one another and changing relative positions throughout the cable length.
Traditional modular plugs are well suited for terminating ribbon type cables. Typically, these plugs are of a dielectric, such as plastic, structure in which a set of terminals are mounted side by side in a set of troughs or channels in the plug body such that the terminals match the configuration of the conductors in the cable connected thereto. When the plug is inserted into a jack, the terminals will electrically engage jack springs inside the jack to complete the connection.
A common problem found in these modular plugs is for the conductors to pull away or be pulled away from the terminals inside the plug structure. This can be caused by persons accidentally pulling on the cable, improperly removing the plug from a jack or merely from frequent use. To alleviate the stress on the connections between the conductors and the plug terminals, prior inventors have included an anchoring member in the housing of the dielectric structure. In these designs, the dielectric structure, i.e., the plug, contains a chamber for receiving the cable. The cable is then secured within the chamber via pressure exerted upon the cable jacket by the anchoring member in conjunction with one or more of the chamber walls. U.S. Pat. Nos. 5,186,649 and 4,002,392 to Fortner, et al. and Hardesty contain examples of such strain relief apparatus.
While these modular plugs have been effective in providing strain relief to ribbon type cables, standard round cables or cords pose additional strain relief problems. For example, to terminate a round cable carrying four conductor pairs with an existing modular plug requires the following steps: First, the cable or cord jacket must be stripped to access the enclosed conductors. Next, because the conductors in a conductor pair are generally twisted around one another, the twist must be removed and the conductors oriented to align with the required interface. Aligning the conductors usually involves splitting the conductors in at least one of the pairs and routing these over or under conductors from other pairs while orienting all the conductors in a side-by-side plane. Once the conductors are aligned in a plane, they may be joined to the terminals in the plug. However, the orientation process can result in various conductors of different pairs crossing over each other, thereby inducing crosstalk among the several conductor pairs.
This process of terminating a round cable introduces significant variability in connecting the conductors to the plug terminals and places additional strain on the connections between the conductors and the plug terminals. Because the individual conductors in a conductor pair are often twisted around one another and the conductor pairs themselves are often twisted around one another, the conductor configuration a technician sees when the cable is cut changes based on the longitudinal position of the cut in the cable. Thus, for each assembly, the technician must determine the orientation of the cable first and then follow the steps discussed above to translate that orientation into a side-by-side, generally planar pattern to match the configuration of the terminals in the plug. Moreover, the necessity of splitting the conductors in at least one of the pairs, which is an industry standard, presents another potential for error in making the connections to the plug terminals. In addition, orienting the conductor positions from an essentially circular arrangement into a planar arrangement places additional stress on the conductor-terminal connections.
U.S. Pat. No. 5,496,196 to Winfried Schachtebeck discloses a cable connector in which the connector terminals are arranged in a circular pattern to match more closely the arrangement of conductors held in a round cable. However, the Schachtebeck invention attempts to isolate each individual conductor and apparently requires all conductor pairs to be split before termination to the connector.
Another problem that has plagued modular plug terminated cables of any type is crosstalk between the communication channels represented by the conductor pairs. The jack springs, conductors, and the plug terminals near the jack springs are generally quite close to, and exposed to, one another providing an opportunity for electrical signals from one channel, i.e. conductor pair, to become coupled to another channel, i.e., crosstalk. Crosstalk becomes particularly acute when the conductors are carrying high frequency signals, and interferes with signal quality and overall noise performance. Furthermore, it is often difficult to ensure proper conductive contact between the jack springs and the conductors, which can also be a source of noise.
In addition, the economic aspects of the prior art necessity for the installer to separate out the twisted pairs of conductors and route them to their proper terminals in the plug are of considerable moment. Even if the installer, splicer, or other operator is accurate in the disposition of the conductors, the time consumed by him or her in achieving such accuracy is considerable. Thus, in a single work day, the time spent in properly routing the conductors can add up to a large amount of time, hence money. Where it is appreciated that thousands of such connections are made daily, involving at least hundreds of installers, it can also be appreciated that any reduction in time spent in mounting the plug can be of considerable economic importance.
Accordingly, there exists a need for a high frequency, modular plug that can terminate a standard round cable and that provides a straightforward interface between the conductors in the cable and the plug terminals, involving considerably less assembly time than heretofore, while simultaneously providing strain relief to the cable. In addition, it is desirable that such a plug be capable of optimizing crosstalk through selective tuning. In this context, optimization means reducing crosstalk in the plug or providing a predetermined level of crosstalk to match the requirements of a jack designed to eliminate an expected crosstalk level.